On 02/04/2015 03:04 AM, Li, Chen wrote:

Hi list,

For generic driver, there is a flag named “connect_share_server_to_tenant_network” in manila/share/drivers/service_instance.py.

When it set to True, share-server(nova instance) would be created directly on the “share-network”.

When it set to False, the subnet within share-network must connected to a router, and then manila would create its own subnet and connect to the router too, and start share-server in manila’s subnet.

Based on https://wiki.openstack.org/wiki/Manila/Networking#Gateway_Mediated, I assume the difference here is L2 vs L3 connectivity.

But, I wander whether there are some other reasons for generic driver to support this flag.

So, my question here is:

As an cloud admin, what I need to consider to help me figure out what value I should set for this flag ?

L3 connectivity tends to be dramatically more efficient in a larger cloud because it limits the size of the broadcast domains. If you try to use L2 connectivity between the share server and all its clients, and any of those machines are separately in the physical world (separate racks, separate aisles, separate datacenters) then all your ARP traffic, etc, is traversing backbone links.

The only benefit to L2 connectivity that I'm aware of is a potential performance improvement by removing the (virtual) router as a bottleneck.

-Ben Swartzlander

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